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git-subtree-dir: torch/lib/THNN git-subtree-mainline:c3f0c1e2e0git-subtree-split:4fe7059a31
43 lines
1.2 KiB
C
43 lines
1.2 KiB
C
#ifndef TH_GENERIC_FILE
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#define TH_GENERIC_FILE "generic/SoftPlus.c"
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#else
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void THNN_(SoftPlus_updateOutput)(
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THNNState *state,
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THTensor *input,
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THTensor *output,
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real beta,
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real threshold)
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{
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THTensor_(resizeAs)(output, input);
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// f(x) = 1/beta * log(1 + exp(beta * x))
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TH_TENSOR_APPLY2(real, output, real, input, \
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*output_data = (*input_data * beta) > threshold ? *input_data : THLog1p(exp(*input_data * beta)) / beta;
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);
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}
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void THNN_(SoftPlus_updateGradInput)(
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THNNState *state,
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THTensor *input,
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THTensor *gradOutput,
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THTensor *gradInput,
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THTensor *output,
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real beta,
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real threshold)
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{
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THTensor_(resizeAs)(gradInput, output);
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// d/dx[log(1+exp(k*x))/k] = exp(kx) / (exp(kx) + 1)
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// SINCE
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// y = (1/k)*log(1+exp(k*x)) --> x = (1/k)*log(exp(k*y)-1)
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// THEREFORE:
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// d/dx(f(x)) = (exp(k*y) - 1) / exp(k*y)
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TH_TENSOR_APPLY3(real, gradInput, real, gradOutput, real, output,
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real z = exp(*output_data * beta);
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*gradInput_data = (*output_data * beta) > threshold ? *gradOutput_data : *gradOutput_data * (z - 1.)/z;
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);
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}
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#endif
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